Buggy code:
public class HttpHeaders implements Serializable , MultiValueMap < String , String > { private static final long serialVersionUID = - 8578554704772377436L ; public static final String ACCEPT = "Accept" ; public static final String ACCEPT_CHARSET = "Accept-Charset" ; public static final String ALLOW = "Allow" ; public static final String CACHE_CONTROL = "Cache-Control" ; public static final String CONNECTION = "Connection" ; public static final String CONTENT_DISPOSITION = "Content-Disposition" ; public static final String CONTENT_LENGTH = "Content-Length" ; public static final String CONTENT_TYPE = "Content-Type" ; public static final String DATE = "Date" ; public static final String ETAG = "ETag" ; public static final String EXPIRES = "Expires" ; public static final String IF_MODIFIED_SINCE = "If-Modified-Since" ; public static final String IF_NONE_MATCH = "If-None-Match" ; public static final String LAST_MODIFIED = "Last-Modified" ; public static final String LOCATION = "Location" ; public static final String ORIGIN = "Origin" ; public static final String PRAGMA = "Pragma" ; public static final String UPGRADE = "Upgrade" ; private static final String [ ] DATE_FORMATS = new String [ ] { "EEE,<seq2seq4repair_space>dd<seq2seq4repair_space>MMM<seq2seq4repair_space>yyyy<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>zzz" , "EEE,<seq2seq4repair_space>dd-MMM-yy<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>zzz" , "EEE<seq2seq4repair_space>MMM<seq2seq4repair_space>dd<seq2seq4repair_space>HH:mm:ss<seq2seq4repair_space>yyyy" } ; private static TimeZone GMT = TimeZone . getTimeZone ( "GMT" ) ; private final Map < String , List < String > > headers ; private HttpHeaders ( Map < String , List < String > > headers , boolean readOnly ) { } public HttpHeaders ( ) { } public static HttpHeaders readOnlyHttpHeaders ( HttpHeaders headers ) { } public void setAccept ( List < MediaType > acceptableMediaTypes ) { } public List < MediaType > getAccept ( ) { } public void setAcceptCharset ( List < Charset > acceptableCharsets ) { } public List < Charset > getAcceptCharset ( ) { } public void setAllow ( Set < HttpMethod > allowedMethods ) { } public Set < HttpMethod > getAllow ( ) { String value = getFirst ( HttpHeaders . ALLOW ) ; <START_BUG> if ( value != null ) { <END_BUG> List < HttpMethod > allowedMethod = new ArrayList < HttpMethod > ( 5 ) ; String [ ] tokens = value . split ( ",\\s*" ) ; for ( String token : tokens ) { allowedMethod . add ( HttpMethod . valueOf ( token ) ) ; } return EnumSet . copyOf ( allowedMethod ) ; } else { return EnumSet . noneOf ( HttpMethod . class ) ; } } public void setCacheControl ( String cacheControl ) { } public String getCacheControl ( ) { } public void setConnection ( String connection ) { } public void setConnection ( List < String > connection ) { } public List < String > getConnection ( ) { } public void setContentDispositionFormData ( String name , String filename ) { } public void setContentLength ( long contentLength ) { } public long getContentLength ( ) { } public void setContentType ( MediaType mediaType ) { } public MediaType getContentType ( ) { } public void setDate ( long date ) { } public long getDate ( ) { } public void setETag ( String eTag ) { } public String getETag ( ) { } public void setExpires ( long expires ) { } public long getExpires ( ) { } public void setIfModifiedSince ( long ifModifiedSince ) { } @ Deprecated public long getIfNotModifiedSince ( ) { } public long getIfModifiedSince ( ) { } public void setIfNoneMatch ( String ifNoneMatch ) { } public void setIfNoneMatch ( List < String > ifNoneMatchList ) { } protected String toCommaDelimitedString ( List < String > list ) { } public List < String > getIfNoneMatch ( ) { } protected List < String > getFirstValueAsList ( String header ) { } public void setLastModified ( long lastModified ) { } public long getLastModified ( ) { } public void setLocation ( URI location ) { } public URI getLocation ( ) { } public void setOrigin ( String origin ) { } public String getOrigin ( ) { } public void setPragma ( String pragma ) { } public String getPragma ( ) { } public void setUpgrade ( String upgrade ) { } public String getUpgrade ( ) { } public long getFirstDate ( String headerName ) { } public void setDate ( String headerName , long date ) { } @ Override public String getFirst ( String headerName ) { } @ Override public void add ( String headerName , String headerValue ) { } @ Override public void set ( String headerName , String headerValue ) { } @ Override public void setAll ( Map < String , String > values ) { } @ Override public Map < String , String > toSingleValueMap ( ) { } @ Override public int size ( ) { } @ Override public boolean isEmpty ( ) { } @ Override public boolean containsKey ( Object key ) { } @ Override public boolean containsValue ( Object value ) { } @ Override public List < String > get ( Object key ) { } @ Override public List < String > put ( String key , List < String > value ) { } @ Override public List < String > remove ( Object key ) { } @ Override public void putAll ( Map < ? extends String , ? extends List < String > > m ) { } @ Override public void clear ( ) { } @ Override public Set < String > keySet ( ) { } @ Override public Collection < List < String > > values ( ) { } @ Override public Set < Entry < String , List < String > > > entrySet ( ) { } @ Override public boolean equals ( Object other ) { } @ Override public int hashCode ( ) { } @ Override public String toString ( ) { } }

Fix:
if ( ! ( StringUtils . isEmpty ( value ) ) ) {